The role of optical prescription laboratories is to deliver lenses to professional customers, such as opticians, independent optometrists, wholesalers and optical chain stores, as quickly as possible. Optical prescription laboratories must produce lenses having the power prescribed in a received order within a certain tolerance. The Semi-Finished (SF) lens blanks used to produce prescription lenses in prescription laboratories have a given front side design that is manufactured under certain tolerances. Due to deviations in the surfacing process in the prescription laboratories, the optical power and optical design achieved by surfacing lenses is not always perfectly on target. When the difference between the prescription optical power and the achieved power is outside of predetermined tolerances, the lens is scrapped, thereby reducing the optical prescription laboratory's industrial yields.
Presently, statistical analysis is performed manually by process engineers in optical prescription laboratories to determine the distribution of lens power deviations between the nominal optical powers and the achieved optical powers. The objective of this analysis is to try to determine whether there is a consistent shift in the optical deviations for which a compensation may be applied to increase the optical prescription laboratory's yields. Using this statistical analysis, the process engineer may determine the average deviation and then statically define compensations to be applied in a Lens Design System (LDS) or optical calculator.
As for design measurements, no systematic per lens design analysis is currently performed in prescription laboratories. This manual work is therefore limited to far vision optical power deviations and is very cumbersome as it requires a good understanding of optical product industrial performances and statistical analysis. It is also limited to the LDS calculators for which the prescription laboratory is able to access the configuration system.